Process for the production of lightweight cellular composites of wood waste and thermoplastic polymers

ABSTRACT

The invention is directed at a composite material comprising a product of a combination of materials. The combination of materials comprises an inorganic filler comprised of ceramic cenospheres, a thermoplastic polymer and a coupling agent comprised of at least one fatty acid having at least 16 carbon atoms and at least one rosin acid having at least 16 carbon atoms. The combination may further comprise an organic filler comprised of cellulosic material and wherein the thermoplastic polymer has a melt temperature of less than the char temperature of the organic filler. The invention is further directed at a process for producing the composite material comprising the step of combining the components at a temperature of greater than or equal to the melt temperature of the thermoplastic polymer. Where the components include the organic filler, the process temperature is less than the char temperature of the organic filler.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 60/022,265 filed Jun. 22, 1996.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 60/022,265 filed Jun. 22, 1996.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a relatively lightweight composite material, and a process for preparing the composite, wherein the composite material is a product of a combination of materials comprising an inorganic filler, a thermoplastic polymer and a coupling agent. The inorganic material is preferably comprised of ceramic cenospheres. In addition, the combination of materials preferably further comprises an organic filler. The organic filler is preferably comprised of co-mingled wood fibers and a thermoset binding polymer.

BACKGROUND OF THE INVENTION

Lightweight plastics composites comprise a versatile family of relatively low density, cellular materials which are made in a variety of processes. Organic and inorganic fillers are typically added to plastics to modify or improve one or more properties of the plastic, thereby making the plastic composite more suitable for a particular application.

For instance, for the purposes of density and/or for the enhancement of insulation properties, the ideal filler is voids. In the plastics industry, plastics that contain voids (cells) are classified as foams. Depending on the degree of foaming, that is, the volume fraction of the foam making up the voids, the properties of such materials may be remarkably different from the basic material. Foaming agents, more commonly known as blowing agents, are chemicals that can be incorporated into the plastic, that lead to the development of cells through the release of a gas at the appropriate time during processing. The amount and types of blowing agents influences the density of the finished product by its cell structure. In essence, these composites are polymers which have typically been expanded by a gas in volume such that they have a uniformly cellular structure which can look like an extremely fine honeycomb or a mass of very tiny ping-pong balls fused together. The cells of some foamed plastics are large enough to be seen, while cells in others are so fine that a microscope is needed.

The development of a cellular structure in a thermoplastic polymer can be enhanced by the aid of a nucleating agent. Nucleated polymers tend to have a finer and more consistent cell size than unnucleated ones. Coarse cells tend to be more brittle than finer cell structures. Conventional nucleating agents can be roughly classified as inorganic additives, such as talc, silica, koalin, and organic salts of specific acids or pigments.

As well, interest in the plastics industry has been focused upon the use of lower cost organic and inorganic fillers for extending and reinforcing thermoplastics. With respect to the inorganic fillers, an emphasis has been placed on the utilization of fillers such as glass fiber, calcium carbonate, clay, talc, wollastonite, silica and mica. These aforementioned fillers are all inorganic minerals that tend to have relatively high specific gravities. Thus, the resultant composite does not tend to be particularly lightweight. Further, in most cases, these fillers tend to require some pre-treatment in order to be compatible with the thermoplastic polymers they are blended with, thus contributing to a higher cost of the composite material.

Specifically, the common inorganic fillers utilized at present, such as calcium carbonate and glass fibers, require beneficial surface treatment to improve adhesion, lubrication and homogenous mixing with the thermoplastic polymer or resin component. For example, calcium carbonate generally requires a precoating of a coupling agent such as a stearate for blending with rigid Polyvinyl Chloride resins. Further, some applications of flue gas residue fly ash as a filler to thermoplastic Polyvinyl Chloride require the surface treatment of the fly ash with a high cost water system amino-vinyl type silane coupling agent to improve the fillers oil absorption, particle surface pH control and adhesion to the polymer. This is important since the viscosity of filler loaded resins are affected by pH controlled reactions between the filler particle surfaces and the plastic matrix.

In recent times, pulverized coal has become the primary fuel for burning in electric utility steam boilers for the generation of electricity, with hundreds of millions of tons of coal consumed annually. Approximately 10% of the coal burned constitutes inorganic matter which is fused in combustion and carried with the flue (exhaust) gas as the carbon is consumed by oxidation. The flue gas cools as it flows out of the steam generators, and the inorganic matter takes the form of spherical ceramic particles typically in the range of between about 1 to 200 microns. The particles are then captured by electrostatic precipitators and collected in hoppers or disposed of in lagoons. These particles are known as cenospheres and are comprised primarily of a calcinated clay.

Environmental considerations play a key role in the aggressive drive for finding applications for this inorganic residue waste material. Some forms of flue gas residue, such as the fly ash derivative, have been used in various products such as light weight concrete, cement, brick, grout, protective coatings and flowable fill. The cenosphere fraction of the fly ash is about 20% by volume of the total fly ash residue. However, the utilization of the cenosphere form of the flue gas residue has had limited applications, resulting in concerns with respect to the disposal of the cenosphere fraction.

More particularly, the addition of the ceramic cenospheres fraction of flue gas residue fly ash as a filler to thermoplastic and thermoset resinous materials has received little attention by the industry. The primary applications focus upon adding the cenospheres to act as a thickening agent for polyesters, epoxy and other liquid thermosets to enable these composites to become more "putty-like" and more easily spread, such as in autobody repair fillers. Further, more recent research indicates that the use of cenospheres in moldings of polyester and phenolic resins may result in improved or comparable mechanical properties as compared to conventional fillers such as calcium carbonate.

With respect to organic fillers, the supply and cheapness of wood fiber on a world-wide basis, as well as its other advantages, has also made wood fibers a desirable material for filler/reinforcing in combination with thermosetting or thermoplastic materials.

Conventional wood composites comprised of wood fibers and thermosetting polymers, such as plywood and fiberboard, which are offered on the market today tend to suffer from low moisture resistance due to the hydrophilic nature of the wood. For this reason, amongst others, during the last several years, interest has grown in the combination of wood fibers with thermoplastic matrices for the production of composite materials, particularly for low cost/high volume applications. Using a thermoplastic polymer in the composite has been found to result in an improvement in the water resistance and other properties of the composite material.

Further, the development of wood fiber and thermoplastic composites has occurred because wood-derived fillers or reinforcement for thermoplastic polymers may have several further advantages. For instance, the use of wood fibers as filler and reinforcement for thermoplastics may result in a composite material having a lower cost to produce, a lower density, a greater tensile modulus (which results in lower filler damage during processing), and less abrasiveness to processing equipment as compared to other fillers or reinforcing materials on the market for thermoplastics. In addition, wood fiber fillers are derived from a renewable resource.

However, the use of an organic wood fiber filler, and various inorganic fillers, in combination with thermoplastics has been somewhat limited mainly as a result of difficulties experienced in dispersing the filler, which tends to be naturally hydrophilic, in the thermoplastic polymer matrix, which tends to be naturally hydrophobic. In addition, as a result of the hydrophilic nature of the filler and the hydrophobic nature of the thermoplastic, there appears to be a weak interaction therebetween. Insufficient dispersion and weak interactions may result in poor adhesion (wettability and particle-bonding), and in consequence, inferior mechanical properties in the resultant composite materials.

More particularly, because the filler tends to be insoluble in the thermoplastic polymer matrix, a polymer matrix interface is created. The interface/interphase region strongly affects the end properties of the composite material. The interface is the surface between the two phases, whilst the interphase is defined as the region between the filler and the thermoplastic polymer matrix. Poor interaction between the filler and the polymer matrix decreases the interfaces between the phases.

Several approaches have been developed for improving the compatibility of wood fiber fillers and the thermoplastic polymer matrix. More particularly, emphasis has been placed on improving the interfacial adhesion between the hydrophilic wood particles and the hydrophobic thermoplastic polymer matrix. Two primary approaches have been used: (1) modification of the wood surface before processing; and (2) use of a compatibilizing or coupling agent during compounding.

Many different approaches are reported in the literature for surface treatment of the wood, for example, coating and grafting of the wood fibers. The basic method employed is to chemically modify the wood filler component prior to compounding.

With respect to the use of compatibilizing agents, referred to in the industry as coupling agents, it has been determined that the adhesion between the wood fibers and the synthetic polymer can be improved when the coupling agent is added during processing. Coupling agents may act to modify the interface between the wood fibers and the thermoplastic polymer by interacting therewith and forming a link or bond between the components. Thus, the use of coupling agents may enhance the inherently poor attraction between the polar wood and the non-polar thermoplastic component.

The "coupling agents" previously used in the industry in the production of wood fiber-thermoplastic polymer composite materials cover a broad range of complex polymers, such as: maleic anhydride polyethylene (MAPE)/polypropylene (MAPP); styrene-butadiene-styrene; carboxylic wax; ionomer modified polyethylene; and low molecular weight polypropylenes. However, these types of coupling agents may be expensive to use or difficult to disperse within a matrix mixture.

There is therefore a need in the industry for a composite material comprised of relatively low cost components and exhibiting comparable or improved properties as compared to known composites in the market. More particularly, there is a need for an improved composite material comprised of an inorganic filler, or a combination of inorganic and organic fillers, and a thermoplastic polymer There is also a need for a relatively cost effective coupling agent for use in the improved composite material to enhance the properties thereof. Further, there is a need for a relatively lightweight composite material, as compared to known composites. Finally there is also a need for a process for producing the composite material.

SUMMARY OF THE INVENTION

The within invention relates to a relatively lightweight composite material comprising a product of a combination of materials and a process for producing the same. The combination of materials comprises an inorganic filler comprised of a relatively lightweight material, a thermoplastic polymer and a coupling agent. Further, the combination of materials may also comprise an organic material and/or a blowing agent. Preferably, the combination of materials are relatively low cost and the composite material exhibits comparable or improved properties as compared to known composites in the market. Further, the within invention relates to a relatively cost effective coupling agent for enhancing the properties of the composite material.

More particularly, in the preferred embodiment, the within invention relates to the production of a new relatively lightweight composite material using an inorganic filler, preferably comprised of ceramic cenospheres, in a matrix of a thermoplastic polymer. Further, the composite material may also be produced using the inorganic filler in combination with an organic filler, preferably comprised of a cellulosic material, in the thermoplastic polymer matrix.

The bonding or adhesion of the components, and the distribution of the components throughout the composite, are aided by a coupling agent. The coupling agent is comprised of at least one high molecular weight fatty acid and at least one high molecular weight rosin acid Preferably, the coupling agent is comprised of tall oil. The coupling agent is believed to improve dispersion of the fillers into the thermoplastic polymer and to improve the processing and other properties of the composite material.

Finally, the within invention relates to the use of a blowing agent in combination with the aforementioned components used in the production of the composite material.

In a first aspect of the invention, the invention is comprised of a composite material comprising a product of a combination of materials. The combination of materials comprises: an inorganic filler comprised of ceramic cenospheres; a thermoplastic polymer; and a coupling agent comprised of at least one fatty acid having at least 16 carbon atoms and at least one rosin acid having at least 16 carbon atoms.

In a second aspect of the invention, the invention is comprised of a process for producing a composite material. The process is comprised of the step of combining an inorganic filler comprised of ceramic cenospheres, a thermoplastic polymer and a coupling agent comprised of at least one fatty acid having at least 16 carbon atoms and at least one rosin acid having at least 16 carbon atoms, wherein the combining step is performed at a temperature of greater than or equal to the melt temperature of the thermoplastic polymer.

In the first aspect of the invention, the combination of materials preferably further comprises an organic filler comprised of cellulosic material and wherein the thermoplastic polymer has a melt temperature of less than the char temperature of the organic filler In the second aspect of the invention, the combining step preferably further comprises combining an organic filler comprised of cellulosic material with the inorganic filler, the thermoplastic polymer and the coupling agent and wherein the combining step is performed at a temperature greater than or equal to the melt temperature of the thermoplastic polymer and less than the char temperature of the organic filler.

Further, in the first and second aspects of the invention, the coupling agent may be comprised of any suitable percentages by weight of the fatty acids and rosin acids capable of performing the function of the coupling agent. However, preferably, the coupling agent is comprised of between about 10 to 55 percent by weight of the fatty acids and of between about 5 to 50 percent by weight of the rosin acids. In the preferred embodiment, the coupling agent is comprised of between about 35 to 55 percent by weight of the fatty acids and of between about 25 to 50 percent by weight of the rosin acids.

Further, the coupling agent may be comprised of any percentage by weight of unsaponifiables which does not significantly interfere with the functioning of the coupling agent. However, preferably, the coupling agent is comprised of less than about 40 percent by weight of unsaponifiables. In the preferred embodiment, the coupling agent is comprised of less than about 20 percent by weight of unsaponifiables.

Preferably, the coupling agent is comprised of a tall oil. The tall oil may be naturally or synthetically produced. In the preferred embodiment, the tall oil is a depitched tall oil.

Further, in the first and second aspects, the organic filler may be comprised of any suitable cellulosic material capable of performing the function of the organic filler and reinforcing the composite material such that the composite material exhibits the desired properties. For instance, the organic filler may be comprised of wood fibers However, in the preferred embodiment, the organic filler is comprised of co-mingled wood fibers and a thermoset binding polymer.

The organic filler may have any suitable particle size or moisture content compatible with the desired properties of the composite material and the process for producing it. Preferably, the organic filler has a particle size of less than or equal to about United States of America standard sieve size 40 mesh. Further, the moisture content of the organic filler is preferably between about 2 and 6 percent by weight.

Any suitable thermoplastic polymer having a melt temperature less than the char temperature of the organic filler may be used to produce the composite material. However, preferably, the thermoplastic polymer is comprised of a polyolefin having a melt temperature of less than about 390 degrees Fahrenheit. In the preferred embodiment, the polyolefin is selected from the group consisting of polyethylene, polypropylene and polyvinyl chloride. More preferably, the polyolefin is comprised of polyvinyl chloride.

Further, in the first aspect of the invention relating to the composite material, any amount of the coupling agent able to perform the purpose or function of the coupling agent and to achieve the desired properties of the composite material may comprise the combination of materials. However, the combination of materials is preferably comprised of the coupling agent in an amount of between about 0.5 to 10 percent by weight of the organic filler and the inorganic filler. In the preferred embodiment, the combination of materials is comprised of the coupling agent in an amount of between about 0.5 to 5 percent by weight of the organic filler and the inorganic filler.

As well, in the first aspect, any amount of the organic filler and/or the inorganic filler capable of performing the functions of the filler or fillers and reinforcing the composite material such that the composite material exhibits the desired properties may be used. Preferably, the combined organic and inorganic fillers comprise between about 10 and 80 percent by weight of the composite material. Further, in the preferred embodiment, the combined organic and inorganic fillers comprise between about 25 and 70 percent by weight of the composite material.

In addition, in the first aspect, the organic filler preferably comprises between about 10 to 90 percent by weight of the combined organic and inorganic fillers and the inorganic filler preferably comprises between about 90 to 10 percent by weight of the combined organic and inorganic fillers. In the preferred embodiment, the organic filler comprises about 50 percent by weight of the combined organic and inorganic fillers and the inorganic filler comprises about 50 percent by weight of the combined organic and inorganic fillers.

In the first aspect, any amount of thermoplastic material capable of performing the function of the thermoplastic polymer such that the composite material exhibits the desired properties may be used. However, preferably, the thermoplastic polymer comprises between about 30 and 75 percent by weight of the composite material.

Finally, in the first aspect, the combination of materials may be further comprised of any suitable blowing agent compatible with the other components used to produce the composite material. More particularly, the blowing agent is preferably comprised of a chemical blowing agent. Any effective amount of the blowing agent may be used which is able to achieve the desired properties of the composite material. However, preferably, the combination of materials is comprised of the blowing agent in an amount of between about 0.2 and 5 percent by weight of the thermoplastic polymer.

In the second aspect, the combination of materials may be combined in any order either consecutively or concurrently. However, where only an inorganic filler is used in the combination of materials, the combining step is preferably comprised of the steps of first mixing the inorganic filler with the coupling agent such that the coupling agent substantially wets the inorganic filler to produce a wetted filler and second mixing the thermoplastic polymer with the wetted filler such that the thermoplastic polymer is substantially homogeneously blended with the wetted filler to produce the composite material. Where the combination of materials includes both an organic and an inorganic filler, the combining step is preferably comprised of the steps of first mixing the inorganic filler and the organic filler with the coupling agent such that the coupling agent substantially wets the inorganic filler and the organic filler to produce a wetted filler and second mixing the thermoplastic polymer with the wetted filler such that the thermoplastic polymer is substantially homogeneously blended with the wetted filler to produce the composite material.

The first mixing step may be comprised of mixing any amount of the coupling agent able to perform the purpose or function of the coupling agent and to achieve the desired properties of the composite material. Preferably, the first mixing step is comprised of mixing an amount of the coupling agent of between about 0.5 to 10 percent by weight of the organic filler and the inorganic filler. In the preferred embodiment, the first mixing step is comprised of mixing an amount of the coupling agent of between about 0.5 to 5 percent by weight of the organic filler and the inorganic filler.

Further, in the second aspect, the first mixing step may be comprised of mixing any amount of the inorganic filler or a combination of the organic and inorganic fillers capable of performing the function of the filler or fillers and reinforcing the composite material such that the composite material exhibits the desired properties. Preferably, the first mixing step is comprised of mixing an amount of the inorganic filler, or an amount of the combined organic and inorganic fillers, of between about 10 and 80 percent by weight of the composite material. In the preferred embodiment, the first mixing step is comprised of mixing an amount of the inorganic filler, or an amount of the combined organic and inorganic fillers, of between about 25 and 70 percent by weight of the composite material.

In addition, in the second aspect, the organic filler preferably comprises between about 10 to 90 percent by weight of the combined organic and inorganic fillers and the inorganic filler preferably comprises between about 90 to 10 percent by weight of the combined organic and inorganic fillers. In the preferred embodiment, the organic filler comprises about 50 percent by weight of the combined organic and inorganic fillers and the inorganic filler comprises about 50 percent by weight of the combined organic and inorganic fillers.

The second mixing step, in the second aspect of the invention, may be comprised of mixing any amount of the thermoplastic polymer capable of performing the function of the thermoplastic polymer such that the composite material exhibits the desired properties. In the preferred embodiment, the second mixing step is comprised of mixing an amount of the thermoplastic polymer of between about 30 and 75 percent by weight of the composite material.

Further, in the preferred embodiment, the combining step is further comprised of dispersing a blowing agent throughout the thermoplastic polymer prior to the second mixing step. Any suitable blowing agent compatible with the other components used to produce the composite material may be so dispersed. However, preferably, the blowing agent is comprised of a chemical blowing agent. Any effective amount of the blowing agent may be used which is able to achieve the desired properties of the composite material. However, preferably, the combination of materials is comprised of the blowing agent in an amount of between about 0.2 and 5 percent by weight of the thermoplastic polymer.

Finally, in the second aspect, the process is preferably further comprised of the step of extruding the composite material at a temperature of less than 390 degrees Fahrenheit.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a schematic illustration of the filler particle-thermoplastic polymer bonding phenomena of the composite material of the within invention;

FIG. 2 is a schematic illustration of the principles of adhesion mechanisms between the filler particles and the thermoplastic polymer of the within invention, and

FIG. 3 is a schematic illustration of the tall oil rosin acids chemistry.

DETAILED DESCRIPTION

The within invention is directed at a relatively lightweight composite material and a process for process for producing such composite material. The composite material comprises a product of a combination of materials. The combination of materials comprises an inorganic filler, a thermoplastic polymer and a coupling agent. Further, in the preferred embodiment, the combination of materials also comprises an organic filler,and preferably a blowing agent. Because the fillers tend to be insoluble inthe thermoplastic polymer, a polymer matrix interface is created. It is known that he interface/interphase region strongly affects the end properties of the composite material. The interface is the surface betweenthe two phases, whilst the interphase is defined as the region between the filler and the thermoplastic polymer. Two interfaces are present in the composite material--one between the interphase and the filler particle andanother between the interphase and the thermoplastic polymer matrix.

Each of the organic and inorganic fillers tends to be comprised of a naturally hydrophilic or polar material, while the thermoplastic polymer is comprised of a naturally hydrophobic or non-polar material. The coupling agent is believed to modify the interface between the filler particles and the thermoplastic polymer in order to enhance the interfacial adhesion therebetween.

Although the specific mechanism of action of the coupling agent is not fully known, it is believed that FIG. 1 represents a schematic illustration of the bonding phenomena occurring between the inorganic filler particles (4), the organic filler particles (2) and the thermoplastic polymer (1) as a result of the presence of the coupling agent (3) to form the composite material of the within invention. The organic (2) and the inorganic (4) filler particles are encapsulated by thethermoplastic polymer (1) into a substantially homogeneous matrix by the wetting action of the coupling agent (3). More particularly, it is believed that the coupling agent (3) improves the dispersion of the filler(2,4) in the thermoplastic polymer (1) and improves the adhesion occurring between the adjacent surfaces of the filler particles (2,4) and the thermoplastic polymer (1). Adhesion is defined as the adhering together oftwo surfaces so that the stresses can be transmitted between the phases andthereby quantify the work energy required to separate the two phases.

It is further believed that the coupling agent may improve the extrusion processability of the composite material and may promote the development of blowing agent generated voids (5) within the polymer matrix. Particularly, it is further believed that the particular inorganic filler used in the preferred embodiment of the within invention may function as anucleating agent for the development of controlled fine-sized voids in the thermoplastic polymer matrix, in the presence of and propagated by the blowing agent during the final stages of processing the combination of materials.

The specific mechanism for the adhesion between the surfaces is believed tobe a result of adsorption, chemical bonding and/or diffusion at the molecular level and electrostatic attraction and/or mechanical interlocking at the micro level. FIG. 2 provides a schematic illustration of each of these adhesion mechanisms.

The inorganic filler may be comprised of any inorganic filler material capable of performing the functions or purpose of the inorganic filler as described herein such that the composite material exhibits the desired properties For instance, the inorganic filler material provides reinforcement to the composite and adds a lightweight component such that the resulting composite material is relatively lightweight. However, in the preferred embodiment, the inorganic filler is comprised of ceramic cenospheres.

Cenospheres are a waste by-product of coal-fired electrical power generation facilities. Approximately 10% of the coal burned constitutes inorganic matter which is fused in combustion and carried with the flue (exhaust) gas as the carbon is consumed by oxidation The flue gas cools asit flows out of the steam generators, and the inorganic matter takes the form of spherical ceramic particles typically in the range of about 1 to 200 microns. The particles are then captured by electrostatic precipitators and collected in hoppers or disposed of in lagoons. Cenospheres are essentially comprised of a calcinated clay. Further, the cenosphere fraction of the fly ash is typically about 20% by volume of thetotal fly ash residue.

Table 1 below sets out a comparison of the typical specific gravity of cenospheres with the typical specific gravities found for other common inorganic fillers. The table shows the potential advantage of using cenospheres in weight reduction of the composite material. Specifically, the lower specific gravity of the cenospheres may translate into a lower density, and thus lighter, composites which may be predicable at a reducedcost per unit volume.

                  TABLE 1     ______________________________________     CENOSPHERES - Comparative Specific Gravities with Other     Common Resin Fillers (Solid Material)     ______________________________________     CENOSPHERES (Coal Combustion Ceramic By-Product                                2.2 gm/cc     CALCIUM CARBONATE          2.7 gm/cc     CLAY                       2.6 gm/cc     TALC                       2.8 gm/cc     ______________________________________

As well, further potential advantages of using cenospheres as the inorganicfiller, as compared to common inorganic fillers, are suggested by the following Table 2 which summarizes the results when a conventional calciumcarbonate filler is replaced by cenospheres in a typical phenolic resin formulation. The samples were comprised of 20% by weight Phenolic resin and 80% by weight filler

                  TABLE 2     ______________________________________     CENOSPHERES - Comparative Tensile & Flexural     Summary Data with Other Common Resin Fillers     Cenospheres combined with Phenolic Resin compared to Phenolic Resin     with Calcium Carbonate Filler (80% by weight Filler and     20% by weight Resin)                        Example 1 Example 2                                          Example 3     PHYSICAL           (Control) Phenolic &                                          Phenolic &     PROPERTIES of      Phenolic &                                  Untreated                                          *Treated     EXAMPLE    Units   Calc. Carb.                                  Cenospheres                                          Cenospheres     ______________________________________     Flexural Strength                psi*10.sup.3                        10.85     13.54   15.35     Flexural Modulus                psi*10.sup.6                        0.76      0.83    0.91     Tensile Strength                psi*10.sup.3                        7.51      7.81    8.57     Tensile Modulus                psi*10.sup.6                        0.76      0.84    0.95     Tensile Elongation                %       1.14      1.17    1.22     HIGH RATE IMPACT SUMMARY DATA     Ultimate Force                Lbs.    248       273     306     Ultimate Energy                in-Lbs  17        19      26     Slope      Lb/in.  671       1,034   1,139     Total Energy                in-Lbs. 47        60      74     Average Thickness                In.     0.103     0.109   0.108     ______________________________________     *Example 3  Depitched Tall Oil Treated Cenospheres (i.e. cenospheres      treated with a coupling agent comprising depitched tall oil, in accordanc     with the within invention).

Any grade of cenospheres capable of performing the purpose of the cenospheres as described herein, such that the desired properties of the composite material are achieved, may be used in the within invention. One available grade of ceramic cenospheres which is acceptable for use in the within invention is produced by TransAlta Utilities, Keephills, Alberta, as described in Table No. 3 and Table No. 4. The cost of this inorganic filler tends to be very economical compared to common fillers, particularly given the limited applications for this filler at the presenttime.

                  TABLE 3     ______________________________________     TYPICAL TRANSALTA UTILITIES CERAMIC CENOSHERE FILLER     Specifications (TransAlta Utilities Inorganic Coal Combustion     Ceramic By-Product)     Particle Size Distribution -     (% by Weight Retained)     Source: University of Alberta                     Mean Particle Size                                   79 Microns     U.S.     Micron               Coarse     Standard Sieve              Equivalent Total Sample                                   Range  Fine Range     ______________________________________      65      212    microns  1.50%     100      150             5.78     150      106            17.71   >      >     200      75             42.44   >84.19%                                            >     270      53             24.04   >      >89.66%     400      38              5.47          >     400      30              3.06     ______________________________________

                  TABLE 4     ______________________________________     TYPICAL TRANSALTA UTILITIES CERAMIC CENOSHERE FILLER     Specifications (TransAlta Utilities Inorganic Coal Combustion     Ceramic By-Product)     ______________________________________     Chemical and Physical     Properties     Source: University of Alberta     Description     Units of Measure                                 Value     ______________________________________     ACIDITY         (pH)        11.00     APPARENT DENSITY                     (g per cc)  0.48-0.50     BULK DENSITY    (g per cc)   0.28     BULK DENSITY    (Lbs. per Cu. Ft.)                                 18     COLOR                       Light Grey     ______________________________________     GENERAL     QUANITATIVE   Sample #1  Sample #2                                       Sample #3     ANALYSIS:     % Oxide    % Oxide  % Oxide     ______________________________________     % OXIDE  Na2O     9.296      9.720  9.035              MgO      0.697      1.019  0.655              Al2O3    30.368     30.580 29.413              SiO2     47.763     47.081 47.496              K2O      0.602      0.484  0.621              CaO      8.532      8.621  10.106              TiO2     0.301      0.229  0.421              Fe2O3    2.441      2.265  2.254              TOTAL: = 99.999     99.999 99.999     ______________________________________

As indicated, the cenospheres are hollow spheres with a thin wall shell. Itis believed that they are preferred as an inorganic filler because the spherical shape tends to have a minimum surface area to volume ratio, resulting in a relatively low viscous drag and improved flow properties. It is further believed that the cenospheres act as lubricants in the composite material and thus, high filler loadings may be achievable without unacceptable increases in viscosity. In addition, the spherical particles reduce the density of the composite material and may exhibit superior stress distribution. An additional side benefit is the tendency of the cenospheres to improve the fire retardency and the insulative and strength characteristics of the composite material.

The organic filler may be comprised of any organic filler material capable of reinforcing the composite material, such that the composite material exhibits the desired properties, and compatible with the process for producing the composite material, as described herein. However, preferably, the organic filler is comprised of a cellulosic material.

Any cellulosic material may be used which is suitable for, and compatible with, its use in a filler-thermoplastic polymer composite and which is capable of performing the purpose or function of the organic filler, as described herein, and thus contributing to the desired properties of the composite material. Particularly, the cellulosic material provides filler and reinforcement to the composite material. Further, the cellulosic material must be compatible with the thermoplastic polymer to be used in the composite material and compatible with the intended process for producing the composite material including the parameters or operating conditions of such process. For instance, the cellulosic material must be capable of withstanding, without significant damage thereto, the physical action or stresses of the process as well as the temperatures required to melt the thermoplastic polymer and achieve a workable composite

In the preferred embodiment, the cellulosic material is comprised of wood fibers or particles of a desired particle size The wood fibers may be untreated, but are preferably treated. Untreated wood fibers have not undergone any chemical processing or treatment or mixing with any other substances such that the natural properties of the wood fibers are unchanged. For instance, the untreated wood fibers may be comprised of sawdust. The sawdust may be derived from any single hardwood or softwood or a combination thereof, but is preferably pine, spruce, fir, poplar, alder, cedar or a mixture thereof.

As stated, in the preferred embodiment, the organic filler is comprised of treated wood fibers. Treated wood fiber is comprised of co-mingled wood fiber of a desired particle size and a thermoset binding polymer. It has been found that the use of treated wood fibers, as compared to untreated wood fibers, in the within invention may improve or enhance the further subsequent bonding or adhesion of the filler with the thermoplastic polymer to produce the new composite material.

The wood fiber component of the treated wood fibers may be derived from anysingle hardwood or softwood or a combination thereof, but is preferably pine, spruce, fir, poplar, alder, cedar or a mixture thereof. Any thermoset binding polymer, compatible for use with the selected wood fibercomponent, may be used singularly or in combination with other thermoset binding polymers. For instance, the thermoset binding polymer may be comprised of phenol formaldehyde, urea formaldehyde, polyisocyanates or combinations thereof. Typically, the thermoset binding polymer is used to improve or enhance the adhesive strength of the wood fiber component and to improve or enhance resistance to delamination from moisture pickup. Furthermore, the thermosetting polymers may also provide improved wetting of the wood fiber component particles.

Preferably, the treated wood fibers, being the co-mingled mixture of wood fibers and thermoset polymer binding, is obtained from waste products. Theuse of waste co-mingled wood fiber-thermoset bonded material may be particularly advantageous given the low cost of the waste material and given that its use may contribute to a solution for a significant waste disposal problem for the industry. Waste co-mingled wood fiber-thermoset bonded material may be derived from the off-cuts and manufacturing scrap resultant from production of plywood, oriented strand board, medium density fiberboard, particle board production or the like and end-use surplus sources.

The precise form of the waste wood fiber-thermoset binder and the specific composition of these products will differ according to the source and the manufacturer. For instance, the thermoset polymer content used in board production may vary from about 3 to 10% by weight for the formaldehyde group of thermoset polymers, and is typically in the range of about 3 to 5% by weight, while the polyisocyanates may vary from about 1 to 6% by weight, and is typically about 2 to 4% by weight.

To prepare the organic filler for use in the preferred embodiment of the invention, the treated wood fiber particles are preferably ground and classified to obtain the desired particle size distribution and desired aspect ratios. The desired particle size distribution and the desired aspect ratios will vary depending upon the desired properties of the resultant composite material and the intended manner of processing the composite material. A typical particle size distribution for treated pine wood fiber filler is shown in Table No 5. Typical generic pine wood fiber properties are shown in Table No.

                  TABLE 5     ______________________________________     SPECIFICATIONS - TYPICAL PINE WOOD FIBER FILLER     Particle Size Distribution - Using Alpine Method (% by Weight Retained)     U.S.     Standard             Micron               (Preferred)     Sieve   Equivalent Grade 2020                                  Grade 4020                                          Grade 14020     ______________________________________     10   Mesh   2000   microns                              Trace % 0%       0%     20          850          0-5.    Trace   0     40          425          40.-80. 0-5.    0     60          250          10.-40. 45.-85. 0     80          180          0-5.    10.-40. 0     100         150          0-5.     0-10.  0     120         125          Not Used                                       0-10.  Trace     140         106          Not Used                                      Not Used                                               0-5.     200         75           Not Used                                      Not Used                                               5.-15.     Balance Retained on Pan                    0-5.       0-10.    85.-95.     ______________________________________

                  TABLE 6     ______________________________________     CHEMICAL AND PHYSICAL PROPERTIES - TYPICAL PINE WOOD     Description     Units of Measure                                  Value     ______________________________________     ACIDITY         (pH)         4.55-4.6     APPARENT DENSITY                     (Lbs. per Cu. Ft.)                                   8.-16.     SPECIFIC GRAVITY                     (g per cc)   0.35-0.50     ASH CONTENT     (% by Weight)                                  0.35%     MOISTURE CONTENT                     (% by Weight)                                  5.-7%     COLOR                        Light Buff     PURITY          Free from Bark, Dirt, Metal & Other                     Foreign Matter     FLASH POINT     (°F.) Not Applicable     AUTOIGNITION TEMP.                     (°F.)   400-500° F.     EXPLOSIVE LIMITS in AIR      40 grams/M3     ______________________________________

Any particle size of the filler and any aspect ratio suitable for, and with, producing the composite material with the desired properties may be her, the desired particle size and aspect ratio may vary depending upon the particular process to be used for the production of the composite material In other words, the particle size and aspect ratio must also be compatible with the production process.

Preferably, the treated wood fibers have a high aspect ratio of at least about 50. However, it may not be necessary to prepare such high aspect ratio wood-polymer initially. In addition, the treated wood fibers preferably have a particle size distribution of less than or equal to about United States of America Standard Sieve size 40 Mesh. Thus, the particle size is preferably less than or equal to about 425 microns.

As well, the treated wood fiber filler may have any moisture content compatible with achieving the desired properties of the composite materialand compatible with the intended manner of processing the composite material In the preferred embodiment, the moisture content of the organic filler is between about 2 and 6 percent by weight of the organic filler.

The proportion of the inorganic filler or the combination of inorganic and organic fillers to be used in the present invention to produce the composite material will vary depending upon a number of factors, includingthe intended manner of processing the composite material, the desired properties of the composite material and its intended use and the quantityand type of the thermoplastic polymer Further, the preferred proportional amount of the inorganic material also depends upon the composition of the organic filler. However, preferably, the composite material is comprised of between about 10 to 80 percent, by weight, of the combined inorganic filler and organic filler. More preferably, the composite material is comprised of between about 15 to 75 percent by weight of the combined inorganic filler and organic filler. In the preferred embodiment, the composite material is comprised of between about 25 to 70 percent by weight of the combined inorganic filler and organic filler.

Prom an economics point of view, it is desirable to have as high a proportional content of the organic and inorganic fillers in the compositematerial as is consistent with achieving desirable strength and other physical properties of the composite material. In the preferred embodiment, the strength and modulus of the resulting new composite have been found to increase with the proportion or percentage of the waste co-mingled wood fiber-thermoset binder filler component, up to about 65 percent by weight of the composite material.

The total or combined filler component, including both organic and inorganic fillers, may be comprised of any proportion of the respective fillers compatible with the desired properties of the composite material. Thus, the organic filler may comprise between 0 and 100 percent of the combined filler and the inorganic filler may comprise between 0 and 100 percent of the combined filler. However, preferably, the organic filler comprises between 0 and 90 percent of the combined filler and the inorganic filler comprises between 0 and 90 percent of the combined filler. In the preferred embodiment, the organic filler comprises about 50percent of the combined filler and the inorganic filler comprises about 50 percent of the combined filler

The thermoplastic polymer of the within invention may be comprised of any suitable thermoplastic polymer compatible with its intended use as described herein. As well, in the preferred embodiment, the process for the production of the composite material requires the heating of the various components of the composite during the combining and mixing thereof. Further, in the preferred embodiment, the composite material undergoes further processing by either extrusion or molding, Thus, the thermoplastic polymer must be capable of withstanding the temperatures associated therewith.

In addition, in order to avoid the charring or burning of the organic filler, the thermoplastic polymer preferably has a melt temperature of less than the char or bum temperature of the specific organic filler beingused in the composite. In particular, wood fibers have been found to have achar temperature of between about 390 and 400 degrees Fahrenheit. Thus, in the preferred embodiment, the thermoplastic polymer has a melt temperatureof less than 390 degrees Fahrenheit. As a result, the combination of materials comprising the composite material may be heated in order to meltthe thermoplastic polymer without resulting in the charring or burning of the organic filler, which tends to detrimentally affect the filler and itsphysical properties.

The specific thermoplastic polymer selected is dependent upon, amongst other factors, the shape and chemical composition of the organic filler material, the particular thermoplastic polymer and the particular properties and characteristics of the coupling agent employed to promote the wetting and synergistic bonding of the filler and thermoplastic polymer into the composite material However, the thermoplastic polymer is preferably of a high molecular weight. More particularly, the thermoplastic polymer is preferably a polyolefin. Further, as indicated above, the polyolefin is selected so that it has a melt temperature of less than 390 degrees Fahrenheit in the preferred embodiment to minimize the likelihood of charring of the filler upon heating of the composite material.

Further, in the preferred embodiment, the polyolefin is preferably one of polyethylene, polypropylene or polyvinyl chloride. Preferably, these preferred polyolefins are not mixed together or used in combination. However, the preferred polyolefins may be used in combination where technically feasible to do so and where the particular polyolefins are compatible for such purpose. For instance, polyethylene may be combined with polypropylene. Further, polyvinyl chloride may be combined with vinylacetate polyethylene.

These preferred polyolefins tend to have a melt temperature of less than about 335 degrees Fahrenheit. Any polyethylene, polypropylene or polyvinylchloride suitable for its intended use as described herein may be used. However, in the preferred embodiment, the polyethylene is a high density polyethylene having a Melt Flow Index (MFI) in the range of 0.4 to 0.6 andthe polypropylene is a co-polymer with similar MFI. These higher molecular weight resins are preferable to effect a more positive entanglement with the wood fiber filler. Alternatively, an amorphous resin such as rigid polyvinyl chloride may be substituted for the polyethylene or polypropylene. Most preferably, the polyolefin is polyvinyl chloride.

The preferable thermoplastic polymers and their typical physical propertiesare shown in Table No.'s 7, 8 and

                  TABLE 7     ______________________________________     Description - THERMOPLASTIC POLYETHYLENE - Typical     Technical Specifications (High Density)                        Typical Value                                   Test Method     ______________________________________     Melting Temperature, °F. (crystalline)                        257-272    (125-133° C.)     Processing Temp. Range, °F.(Extrusion)                        375-475    (191-246° C.)     Coef. of Thermal Expansion( 10-6 In/                        70         ASTM D-696     In/°C.)     Thermal Conductivity (10-4 cal-cm/sec-                        10         ASTM C-177     cm2-°C.)     Tensile Strength at Break, p.s.i..                        2500-4300  ASTM D-638     Elongation at Break, %                        170-800    ASTM D-638     Tensile Yield Strength, p.s.i..                        2800-3900  ASTM D-638     Tensile Modulus, 103 p.s.i..                        136        ASTM D-638     Flexural Modulus, 103 p.s.i.. at 73° F.                        125-175    ASTM D-790     Izod Impact, ft. lb./in.of notch (1/8"                        3.2-4.5    ATSM D256A     thick Spec.)     Hardness, Shore    D63-65     ATSM D-2240     Water Absorption, % (24 Hr                        <0.01      ASTM D-570     Immersion)     Specific Gravity, 20° C. (g/cc)                        0.947-0.955                                   ASTM D-792     ______________________________________

                  TABLE 8     ______________________________________     Description - THERMOPLASTIC POLYPROPYLENE - Typical     Technical Specifications (Copolymer)                        Typical Value                                   Test Method     ______________________________________     Melting Temperature, °F. (crystalline)                        320-335    (160-168° C.)     Processing Temp. Range, °F.(Extrusion)                        400-500    (205-260° C.)     Coef. of Thermal Expansion( 10-6 In/                        68-95      ASTM D-696     In/°C.)     Thermal Conductivity (10-4 cal-cm/sec-                        3.5-4.0    ASTM C-177     cm2-°C.)     Tensile Strength at Break, p.s.i.                        4000-5500  ASTM D-638     Elongation at Break, %                        200-700    ASTM D-638     Tensile Yield Strength, p.s.i..                        3500-4300  ASTM D-638     Tensile Modulus, 103 p.s.i..                        100-170    ASTM D-638     Flexural Modulus, 103 p.s.i.. at 73° F.                        130-200    ASTM D-790     Izod Impact, ft. lb./in.of notch (1/8"                         1.0-20.0  ATSM D256A     thick Spec.)     Hardness, Rockwell R50-96     ATSM D-2240     Water Absorption, % (24 Hr                        0.03       ASTM D-570     Immersion)     Specific Gravity, 20° C. (g/cc)                        0.890-0.905                                   ASTM D-792     ______________________________________

                  TABLE 9     ______________________________________     Description - THERMOPLASTIC POLYVINYL CHLORIDE - Typical     Technical Specifications (Copolymer)                        Typical Value                                   Test Method     ______________________________________     Melting Temperature, °F. (amorphous)                        167-221     (75-105° C.)     Processing Temp. Range, °F.(Extrusion)                        300-415    (148-213° C.)     Coef. of Thermal Expansion( 10-6 In/                         50-100    ASTM D-696     In/°C.)     Thermal Conductivity (10-4 cal-cm/sec-                        3.5-5.0    ASTM C-177     cm2-°C.)     Tensile Strength at Break, p.s.i.                        6000-7500  ASTM D-638     Elongation at Break, %                        40-80      ASTM D-638     Compressive Strength, p.s.i..                        10,000-16,000                                   ASTM D-638     Tensile Modulus, 103 p.s.i..                        350-600    ASTM D-638     Flexural Modulus, 103 p.s.i.. at 73° F.                        300-500    ASTM D-790     Izod Impact, ft. lb./in.of notch (1/8"                         0.4-20.0  ATSM D256A     thick Spec.)     Hardness, Shore    D65-85     ATSM D-2240     Water Absorption, % (24 Hr                        0.04-0.40  ASTM D-570     Immersion)     Specific Gravity, 20° C. (g/cc)                        1.30-1.58  ASTM D-792     ______________________________________

The relative proportions of the fillers and the thermoplastic polymer may vary, but are also dependent upon, amongst other factors, the shape and chemical composition of the filler material, the particular thermoplastic polymer and the particular properties and characteristics of the coupling agent employed to promote the wetting and synergistic bonding of the filler and thermoplastic polymer into the composite material. However, in the preferred embodiment, the thermoplastic polymer comprises between about 30 to 75 percent by weight of the composite material.

The thermoplastic polymer may be used in any suitable form compatible with the process for the production of the composite material. However, the thermoplastic polymer is preferably of a powdered or micropellet form. This form of the thermoplastic polymer is also compatible with the furtherprocessing of the composite material by extrusion as it facilitates a more rapid melt fluxing during the limited time frame of high output rate product extrusion processing conditions.

The coupling agent is selected to facilitate good dispersion and a more even distribution of the filler and the thermoplastic polymer in the composite material and to enhance bonding or adhesion therebetween. Dispersion refers to the degree of mixing in a colloidal system. Good dispersion corresponds to colloidally stable individual particles. Poor dispersion corresponds to an agglomerated filler.

The coupling agent of the within invention is comprised of at least one high molecular weight fatty acid having at least 16 carbon atoms and at least one high molecular weight rosin acid having at least 16 carbon atoms. Each of the fatty acids and the rosin acids performs the functions and has the properties discussed further below. The coupling agent may be comprised of any suitable percentages by weight of the fatty acids and rosin acids capable of performing the function of the coupling agent. However, preferably, the coupling agent is comprised of between about 10 to 55 percent by weight of the fatty acids and of between about 5 to 50 percent by weight of the rosin acids. In the preferred embodiment, the coupling agent is comprised of between about 35 to 55 percent by weight ofthe fatty acids and of between about 25 to 50 percent by weight of the rosin acids.

Further, the coupling agent may be comprised of any percentage by weight ofunsaponifiables, as described below, which does not significantly interferewith the functioning of the coupling agent. However, preferably, the coupling agent is comprised of less than about 40 percent by weight of unsaponifiables. In the preferred embodiment, the coupling agent is comprised of less than about 20 percent by weight.

In the preferred embodiment, the coupling agent is comprised of tall oil. Tall oil is a by-product of the kraft or sulfate pulping process. In the kraft or sulfate pulping process, fatty acids and rosin acids, occurring in pine wood as free acids or their esters, are saponified to their corresponding sodium salts by a cooking liquor. The salts, as well as someneutral materials referred to as unsaponifiables are dissolved or suspendedin the cooking liquor. The American Society for Testing Materials (ASTM) defines tall oil as a "generic name for a number of products obtained fromthe manufacture of wood pulp by the alkali (sulfate) process, more popularly known as the kraft process." Thus, as described further below, tall oil is a mixture of fatty acids, rosin acids and unsaponifiables. However, although the tall oil is preferably "naturally" produced by the process described above, the tall oil may also be synthetically produced for use in the within invention.

The acid number of the tall oil (mg KOH/g sample) is typically used as a criterion of quality. The higher the acid number, the greater the quantityof the free rosin acids and fatty acids which are available, and thus recoverable. Thus, the acid number of the tall oil also determines the functionality of the tall oil acting as a coupling or wetting agent of thefillers and affects the attractive bonding of the fillers and the thermoplastic polymer. In other words, the greater the acid number of the tall oil, the more effective the tall oil tends to be in acting as, and performing the functions of, a coupling agent. In the within invention, the tall oil preferably has an acid number of greater than about 100. In the preferred embodiment, the acid number of the tall oil is between about100 and 175. However, any acid number of the tall oil, and any quantity of rosin and fatty acids therein, sufficient for the tall oil to perform its intended coupling or compatibilizing function may be used.

It is believed that the tall oil used as the coupling agent in the present invention acts as either, or both, a wetting additive and chemical coupling agent for the organic and inorganic filler particles in the matrix. As the dimensional size of the filler particles for use in the composite material decreases, the more difficult the task of dispersing the particles in the thermoplastic polymer tends to become. The tall oil is believed to surround or wet the individual filler particles as the composite is prepared. As a result, the hydrophilic filler particles and the hydrophobic thermoplastic polymer are rendered more compatible and wetting of the filler particles by the thermoplastic polymer is enhanced or facilitated. Wetting is defined as the extent to which a liquid makes contact with a surface. Thus, the tall oil tends to facilitate the dispersion of the filler particles within the thermoplastic polymer, thus contributing to the more even distribution of the components throughout the composite material. For instance, the tall oil has been found to improve the dispersion of the filler particles in the thermoplastic polymer melt upon extrusion.

As stated, in addition to facilitating the wetting of the filler particles by the thermoplastic polymer, the tall oil may facilitate or enhance a chemical reaction between the thermoplastic polymer and the fillers. Specifically, the tall oil may cause or contribute to the formation of relatively strong bonds between the thermoplastic polymer and the filler particles. As a result, the composites have been found to have an increased affinity or adhesion between the filler particles and the thermoplastic polymer.

It is therefore believed that the effectiveness of tall oil as a coupling agent may be related to its ability to form a strongly held hydrophobic wetted surface layer on the fillers that is attractive to the thermoplastic polymer, thereby tending to increase both the effective bonding area and the encapsulation of the filler particles and to chemically and physically interlock the components into the new composite material.

Finally, it has been found that the use of tall oil as the coupling agent tends to improve the extrusion processability of the composite material The tall oil tends to act as a lubricant to the solid state component particulates and to enhance the conveying of the solids mix in the extruder screw channels to effect a more even mixing and maximum heat exposure with the extruder barrel walls to complete the synergistic melt fluxing of the components into the composite material.

As stated, tall oil is a mixture of fatty acids, rosin acids and unsaponifiables. The chemistry of tall oil tends to be complex because both the rosin and fatty acid fractions contain numerous individual compounds. However, details of the chemistry can be simplified by groupingsimilar compounds and by taking into consideration the fact that all of thefatty and resin acids contain the carboxylic acid group and the bulk of them contain double bonds.

The fatty acids present in tall oil are high molecular weight fatty acids. More particularly, the fatty acids are comprised primarily of C₁₈ (18carbon atoms) linear saturated and unsaturated chains with minor amounts ofC₁₆ chains. The tall oil tends to include more than ten different fatty acids of different molecular size, both saturated and unsaturated. The most common fatty acids found in tall oil are palmitic and stearic acids, which are saturated, and oleic and linoleic acids, which are unsaturated. The typical composition of these fatty acids are presented inTable No. 10. In addition to fatty acids, the fatty acid fraction of the tall oil typically contains 1-2% neutrals or unsaponifiables and 1-2% rosin acids.

                  TABLE 10     ______________________________________     MAJOR TALL OIL FATTY ACIDS CHEMISTRY     ______________________________________     Oleic Acid              50%     CH3 (CH2)7 COOH = CH (CH2)7 COOH     LinoIeic Acid,              40%     CH3 (CH2) 4 CH = CHCH2 CH = CH (CH2)7     Non-             COOH     conjugated     Linoleic Acid,              5%      Several isomers present     Conjugated     Stearic Acid              2%      CH3 (CH2) 16 COOH     Palmitic Acid              0.1%    CH3 (CH2) 14 COOH     ______________________________________

It is believed that the fatty acids of the tall oil act primarily as a surfactant to enhance the compatibility of the filler particles and the thermoplastic polymer, as described above. Thus, the fatty acids are believed to facilitate the dispersion and even distribution of the filler particles throughout the thermoplastic polymer.

The rosin acids present in tall oil are also of a high molecular weight, comprised primarily of C₁₆ (16 carbon atoms) and greater. Rosin acidsoccur in tall oil in a number of isomeric forms, nearly all of which have the same basic skeleton: a three-ring fused system with the empirical formula C₂₀ H₃₀ O₂. The most common rosin acids are abietic-type acids, such as levopimaric, palustric, abietic and neoabieticacids, and pimaric-type acids, such as pimaric and isopimaric acids. Some of these rosin acids are shown in FIG. 3. Many other rosin acids may also be included in lesser amounts. The rosin acid fraction of the tall oil mayalso contain up to 3% fatty acids and 3-4% neutrals or unsaponifiables.

It is believed that the rosin acids of the tall oil act primarily as a tackifier to enhance the bonding or adhesion of the filler particles with the thermoplastic polymer, as described above. It is further believed thatthe rosin acids act to soften or dissolve the thermoplastic polymer such that the polymer is able to bond with the filler particles.

The final primary component of tall oil is neutral materials or unsaponifiables. The unsaponifiables typically include high molecular weight fatty alcohols, esters, plant sterols, hydrocarbons and beta-sitosterol. In the preferred embodiment, the tall oil is depitched. Depitching of the tall oil involves the removal of a portion of the pitch and the more volatile unsaponifiables. These components tend to result in a lower quality tall oil and therefore are preferably removed from the tall oil. Depitched tall oil is a product obtained from the distillation of crude tall oil in a fractionating process.

An example of a commercial grade of depitched tall oil acceptable for use in the within invention is produced by B.C. Chemicals Limited, Prince George, B.C., Canada. The depitched tall oil contains reduced contents of unsaponifiables, as described in Table No.

                  TABLE 11     ______________________________________     Description - DEPITCHED TALL OIL     Technical Specifications                        Typical Value                                   Test Method     ______________________________________     ACID NUMBER        154        ASTM D-803     FATTY ACIDS, %     45         ASTM D-803     ROSIN ACIDS, %     35         ASTM D-803     UNSAPONIFIABLES, % 15         ASTM D-803     ASH, %             trace      ASTM D-803     MOISTURE, %        trace      ASTM D-803     VISCOSITY, 600° C., cSt                        26         ASTM D-2170     VISCOSITY, 100° C., cSt                        8          ASTM D-2170     FLASH POINT, °C. (Pensky - Martens                        185        ASTM D-93     Closed Cup     SPECIFIC GRAVITY, 20° C.                        0.97     ______________________________________

The chemical composition of the tall oil and the percentage of fatty acids,rosin acids and unsaponifiables therein tends to vary with the geographicallocation and with the species of trees used in pulping. However, preferably, in the within invention, as described above, the tall oil is comprised of between about 10 to 55 percent by weight of the fatty acids, between about 5 to 50 percent by weight of the rosin acids and less than about 40 percent by weight of unsaponifiables. In the preferred embodimentutilizing depitched tall oil, the depitched tall oil is preferably comprised of between about 35 to 55 percent by weight of the fatty acids, between about 25 to 50 percent by weight of the rosin acids and less than about 20 percent by weight of unsaponifiables.

Any effective amount of coupling agent sufficient for performing its intended functions as described herein may be used. Further, the amount ofthe coupling agent used will vary depending upon the desired properties of the composite material. Thus, the amount of the coupling agent for use in the present invention may vary over wide limits. In addition, the preferred proportional amount of the coupling agent is determined by, amongst other factors, the quantity and type of the thermoplastic polymer used and the composition of the fillers.

Preferably, when using depitched tall oil as the coupling agent, the proportion of coupling agent added is between about 0.5 to 10% by weight, based upon the weight of the combined organic filler and the inorganic filler. In the preferred embodiment, the composite material is comprised of an amount of the coupling agent of between about 5 to 10 percent by weight of the combined organic filler and the inorganic filler.

Finally, where appropriate for the particular intended use of the compositematerial and its desired properties, the composite material may be further comprised of appropriate additional components. For instance, the composite material may be further comprised of antioxidants or inhibitors to enhance the stability of the resultant product or a blowing agent. As well, where appropriate, an additional component of a liquid or dry powdered phenolic resin may be used to enhance the adhesive binding of theresultant final processed end product.

In the preferred embodiment, the combination of materials used to produce the composite material further comprises a blowing agent. Any suitable blowing agent compatible with the other components used to produce the composite material may be used. However, preferably, the blowing agent is comprised of a chemical blowing agent.

Foaming agents, more commonly known as blowing agents, are chemicals that can be incorporated into the thermoplastic polymer and that lead to the development of cells through the release of a gas at the appropriate time during processing. The amount and types of blowing agents influences the density of the finished product by its cell structure.

There are two major types of blowing agents: physical and chemical. Physical blowing agents tend to be volatile liquids or compressed gases that change state during the processing to form a cellular structure. Chemical blowing agents tend to be solids that decompose thermally to formgaseous decomposition products The gases produced are finely distributed inthe thermoplastic melt to provide a cellular structure.

In addition, chemical blowing agents can be divided into two major classifications; organic and inorganic. The organic blowing agents are available in a wide range of different chemistries, physical forms and modification, such as, for example, azodicarbonamide. Inorganic blowing agents are more limited. A typical inorganic blowing agent is comprised ofbicarbonate and citric acid, which evolve carbon dioxide upon decomposition. The blowing agent may be either organic or inorganic, but is comprised of a blend of polycarbonic acids and carbonates in the preferred embodiment. Upon the endothermic decomposition of the blend of polycarbonic acids and carbonates at 320° F., carbon dioxide gas isreleased Further heating during processing to 390° F. will release more gas.

Chemical blowing agents are usually supplied in powder form or pellet form.The specific choice of the blowing agent will be related to the cost, desired cell development and gas yield and the desired properties of the composite material.

In the within invention, the chemical blowing agent is dispersed in the thermoplastic polymer for purposes of density or hardness reduction and toimprove the heat or sound insulation properties. As indicated, the thermoplastic polymer is modified by the formation of voids within the matrix, or cells, by the action of a chemical blowing agent. The blowing agent forms cells through the release of gas at the appropriate time during processing. The blowing agent is a heat-sensitive chemical that undergoes a decomposition reaction upon heating, yielding both gas and solid decomposition products.

Nucleating agents encourage the formation of many small cells. In the within invention, the fine particle cenospheres provide sites within the molten polymer matrix for the new gas phase to form, and thus acts as a nucleating agent. As the gas diffuses through the polymer, the cells grow until an equilibrium is achieved with the polymer melt strength and the internal gas pressure stabilizes to limit the cell size.

The primary consideration for selecting the blowing agent is to match the agent's decomposition temperature with the processing melt temperature of the polymer. In the preferred embodiment using a rigid Polyvinyl Chloride as the thermoplastic polymer, the agent preferably evolves gas at a temperature of from 250° F. to about 350° F. The product of the reaction is a gas mixture consisting mainly of nitrogen and carbon dioxide with lesser amounts of carbon monoxide and ammonia.

Further, the permeability of the blowing agent gas within the polymer and the volume of gas released per unit weight of agent are important factors in selecting the blowing agent. These factors are referred to as the blowing or foaming agent efficiency. Effective blowing agents should yieldat least 100 to 200 cc. of gas (measured at Standard Temp. and Press.) per gram of agent. Depending on the degree of foaming, that is, the volume fraction of the foamed matrix made up of voids, the properties of such endproduct composite materials may be remarkably different from the solid or base thermoplastic polymer.

The range of commercially available chemical blowing agents is extensive. However, it is preferred to select a powdered material with small particlesize and which is compatible with the coupling agent. It has been found that the activation of the blowing agent may be enhanced and promoted by the stearic acid fraction of the tall oil. As well, the dispersion in the dry blend may be aided by the wetting action of the polymer by the tall oil and an enhanced coating of the polymer particles by the blowing agent prior to processing.

The amount or proportion of the blowing agent used in the combination of materials will vary depending upon the type of blowing agent and the desired properties of the composite material. However, preferably, the blowing agent comprises an amount of between about 0.2 and 5 percent by weight of the thermoplastic polymer. In the preferred embodiment, the blowing agent comprises an amount of between about 0.2 and 3 percent by weight of the thermoplastic polymer.

An example of a preferred chemical blowing agent for use in the within invention is Hydrocerol BIH and Hydrocerol BIF (Boehringer Ingelheim KG), available in powder form. The base ingredients of Hydrocerol are bicarbonate and citric acid. Tables No. 12 and 13 illustrate these two examples and their respective properties.

                  TABLE 12     ______________________________________     HYDROCEROL BIH Chemical Blowing Agent     ______________________________________     Application:              Foaming of PVC and Polyolefinic Thermoplastics     Active   Finely Powdered Multicomponent (Bicarbonate & Citric     Ingredients:              Acid)     Characteristics:              Endothermal Decomposition     Physiology:              Conform to German & NA Food Regulations     Supplied As:              White, free-flowing powder - excellent storage stability     Technical Data:              Start of Decomposition - Approximately 140° C.              (284° F.)     Processing:              Optimum Gas Yield-Working Temp. 180-210° C.              (356-410° F.)     Dosage:  For Extrusion - 0.3 to 1.2% ratio by weight of     ______________________________________              polymer

                  TABLE 13     ______________________________________     HYDROCEROL BIF Chemical Blowing Agent     ______________________________________     Application:              Foaming of PVC and Polyolefinic Thermoplastics     Active   Inorganic blowing system with a special particle structure     Ingredients:     Characteristics:              Endothermal Decomposition     Physiology:              Conform to German & NA Food Regulations     Supplied As:              White, free-flowing powder - excellent storage stability     Technical Data:              Start of Decomposition - Approximately 120° C.              (248° F.)     Processing:              Optimum Gas Yield-Working Temp. 170-200° C.              (338-392° F.)     Dosage:  For Extrusion - 0.4 to 2.5% ratio by weight of     ______________________________________              polymer

The present invention is also directed at a process for producing the lightweight composite material as described above. The process may be comprised of a single combining step performed at a specific temperature causing the components to reach a flux state. Specifically, the inorganic filler, the thermoplastic polymer and the coupling agent are measured or proportioned and then combined together at a temperature of greater than or equal to the melt temperature of the thermoplastic polymer, so that thethermoplastic polymer reaches a fluxed state condition. Where the combination of materials also comprises the organic filler, the combining step further comprises combining the organic filler with the other components. In this case, the combining step is performed at a temperaturegreater than or equal to the melt temperature of the thermoplastic polymer and less than the char temperature of the organic filler Any suitable apparatus, device or process for combining the components of the compositematerial at the required temperature may be used. However, preferably a high intensity blender is used.

Preferably, the processing conditions, including the processing temperature, time and manner of combining the components are selected suchthat the combining step results in a substantially uniform or homogeneous composite material, without resulting in any significant thermal or mechanical degradation of the organic filler, the inorganic filler or the thermoplastic polymer. Thus, a high shear agitation is preferably used to combine the components of the composite material.

The components producing the composite material may be combined and mixed together in a single step or any series of steps in order to produce the composite material. For instance, the cenospheres may be added to the thermoplastic polymer and then mixed with the organic filler and the coupling agent. However, in the preferred embodiment, the combining step preferably comprises a first mixing step and a second mixing step. The first mixing step is comprised of mixing the organic filler or the combination of the organic and inorganic fillers with the coupling agent such that the coupling agent substantially wets the filler or fillers to produce a wetted filler. The second mixing step is comprised of mixing thethermoplastic polymer with the wetted filler such that the thermoplastic polymer is substantially homogeneously blended with the wetted filler to produce the composite material.

The organic filler is prepared for use in the composite material, where necessary, by sizing and drying it or taking other steps to achieve other desired specifications or properties. The filler may be so prepared for use using methods, apparatuses and devices known in the industry.

The coupling agent is then added to the fillers at the desired proportion or percentage and the filler-coupling agent mixture is mixed such that thecoupling agent substantially wets the fillers. Any suitable apparatus, device or process for mixing these components may be used. However, preferably a high intensity blender, providing a high shear agitation, is used. It has been found that given that the tall oil is in a liquid state form, it may be readily mixed with the fillers upon intensive blending or mixing.

The first mixing step may be performed for any period of time sufficient toachieve the desired degree of mixing between the fillers and the coupling agent. More particularly, the mixing step is performed for a period of time sufficient to achieve a substantial wetting of the fillers by the coupling agent such that the coupling agent is able to perform its purposeor function as described herein. In the preferred embodiment, the tall oil and the fillers are intensively blended for a period of between about 3 and 15 minutes.

In addition, in the preferred embodiment, in order to enhance the mixing ofthe fillers and the coupling agent, the first mixing step is preferably performed at a sufficiently elevated temperature to achieve this purpose without significantly damaging the filler particles. Specifically, the filler-coupling agent mixture is preferably heated during the first mixingstep to a temperature of between about 150 and 200 degrees Fahrenheit. However, higher temperatures may be used as long as the temperature is less than the char temperature of the organic filler. Alternately, heatingof the mixture during the first mixing step may not be required where sufficient wetting of the fillers is achievable without it. The wetted filler produced by the first mixing step is then preferably cooled to ambient temperature following completion of the first mixing step.

The thermoplastic polymer is preferably prepared for use in the process, such as by the addition of pigments or stabilizers, in a manner known in the industry. In addition, where desired, the chemical blowing agent may be dispersed throughout the thermoplastic polymer. The prepared thermoplastic polymer is subsequently added to the wetted filler and the thermoplastic polymer is mixed with the wetted filler, while being heated,in a manner such that the thermoplastic polymer reaches a flux state and issubstantially homogeneously blended with the wetted filler to produce the composite material.

Specifically, the thermoplastic polymer and wetted filler are heated duringthe second mixing step to a temperature of greater than or equal to the melt temperature of the thermoplastic polymer and less than the char temperature of the organic filler, so that the thermoplastic polymer reaches a fluxed state condition. In the preferred embodiment, the second mixing step is performed at a temperature of less than 390 degrees Fahrenheit, and more preferably, at a temperature of between about 300 and375 degrees Fahrenheit. Any suitable apparatus, device or process for mixing these components at the desired temperature may be used. However, preferably a high intensity blender, providing a high shear agitation, is used.

The second mixing step may be performed for any period of time sufficient to achieve the desired degree of blending between the fillers and the thermoplastic polymer. Although the desired degree of blending may vary depending upon the desired properties of the composite material, the blending step is preferably performed for a period of time sufficient to substantially homogeneously mix the components to produce a substantially homogeneous composite material.

The composite material is then preferably heat processed into the desired end product, such as by molding or extrusion. It has been found that the composite material of the within invention tends to have relatively good extrusion processing characteristics as compared to conventional composites, including improved continuous extrusion of the composite material and enhanced accommodating processing and physical properties.

It is believed that the coupling agent and the inorganic filler may act as lubricants to the solid state component particulates and thus enhance the conveying of the solids mix in the extruder screw charnels to effect a more even mixing and maximum heat exposure with the extruder barrel walls to complete the synergistic melt fluxing of the components into a new lightweight wood fiber-thermoplastic polymer composite product. Reduced torque and energy requirements of the extruder apparatus are also found.

Although the combining and the extruding steps may be performed separately in different processing equipment, alternately, an extruder may be used toperform both of these steps. Specifically, the components of the composite material may be combined together at the desired temperature within the extruder and subsequently extruded. For instance, the components may be flux melted by the extruder at a temperature of less than 390 degrees Fahrenheit, or at a temperature of between about 300 and 375 degrees Fahrenheit. For this purpose, any suitable plasticizing extruder may be used. However, preferably, the extruder is a twin screw extruder apparatushaving a variable rate drive means able to starve feed the composite material continuously into the feed hopper of the extruder.

In order to achieve desirable results from the extrusion process, the composite material should be uniformly heated/melted and well mixed prior to extrusion. Proper melting and mixing requires that the correct screw isused and that sufficient back pressure is present in the barrel to enable optimum fluxing and thermal uniformity. In the preferred embodiment, the extrusion preferably occurs at a back pressure range of between 500 and 2000 psi. Further, a vacuum is preferably applied to the extruder such that volatiles and moisture may be drawn off. Preferably, the negative pressure of the vacuum is in the range of between about 10 to 25 inches ofHg.

A die mounting head and shaping die are affixed to the extruder barrel exitso that the desired end product may be formed. In addition, the extruded product may undergo further conventional processing steps to produce either a flat sheet or profile shape product.

End uses for the new composite material are varied with a primary application as a raw material infeed for extrusion conversion into lightweight flat sheets and panelboards. The composite material may also be extruded into lightweight dimensional profile shapes for the building products industry. The new composite material provides an alternative or replacement for conventional solid plastics, wood fiber-thermoset composites and milled generic wood dimensional mouldings and trims such asare used in the construction, window and door, cabinetry and furniture fabrication industries.

It has been found that not only are the physical properties of tensile strength and elastic modulus improved but also the durability properties of the composite material. As well, products produced from the composite material tend to have an aesthetically pleasing appearance with smooth surfaces and minimum distortion. Furthermore, the production composite material scrap and trims can be reground and re-extruded to yield a product exhibiting little, if any, deterioration in physical properties

EXAMPLES

The invention is further illustrated in the following specific examples.

Where indicated in the examples, the source millwork moulding residues are a co-mingled fine particle wood fiber-thermoset mixture (medium density fiberboard, manufactured by Ranger), obtained from Dartree Group Inc., Edmonton, Alberta, Canada. The source plywood trim and scrap residues are a co-mingled long wood fiber-thermoset mixture (Construction Plywood manufactured by Zeidler) obtained from Zeidler Forest Industries Ltd., also of Edmonton, Alberta, Canada. The thermoplastic polymers used are as illustrated in Tables No. 7, 8 and 9. The Examples are as follows:

Example 1 Typical solid thermoplastic polymers--control component (no additives or fillers).

Example 2 Co-mingled wood fiber-thermoset mixture (treated), thermoplastic PVC polymer and depitched tall oil.

Example 3 Co-mingled wood fiber-thermoset mixture (treated), ceramic cenospheres, thermoplastic PVC polymer and depitched tall oil.

Example 4 Co-mingled wood fiber-thermoset mixture (treated), thermoplastic PVC polymer, depitched tall oil and chemical blowing agent.

Example 5 Co-mingled wood fiber-thermoset mixture (treated), ceramic cenospheres, thermoplastic PVC polymer, depitched tall oil and chemical blowing agent.

Example No. 1 is the basic control thermoplastic polymers providing the base datum for comparison of properties and improvements in a variety of new light weight wood-polymer composites of the within invention as shown in Examples No. 2 through 5,.

    ______________________________________     SOLID THERMOPLASTIC POLYMER S     Example No. 1     Formulation for Typical Polymers for Evaluation Sample Comparisons                         Ratio per                                  Percent                         100 Parts                                  of Total                                        Solid Polymer     COMPONENT    Ref    Mixture  Mix   Specific Gravity     ______________________________________     Rigid Polyvinyl Chloride                         100      100%  1.43  g/cc     H.D. PoIyethyIene   100      100%  0.96  g/cc     Polypropylene       100      100%  0.91  g/cc     Other Additives/Fillers                          0          0  0     ______________________________________

Example No. 2 contains no ceramic cenospheres or chemical blowing agent. This example contains a waste wood fiber-thermoset bonded MDF particleboard moulding sawdust, pre-treated with the wood fiber content being adhesive and pressure bonded by a phenolic formaldehyde thermoset binding component. This organic filler component material is thus referredto as being "treated" and "co-mingled". The organic filler was sized to equivalent generic "un-treated" sawdust grade 4020 specifications as shownpreviously in the Table No. 5. The Thermoplastic Resin is a typical rigid PVC powdered profile extrusion grade formulation. This example divulges a materials blend formulation and the results for comparison of properties and improvements against the solid thermoplastic rigid Polyvinyl Chloride of Example No.

    ______________________________________     WOOD FIBER and THERMOPLASTIC POLYMER     Example No. 2     Formulation for Typical Blend for Evaluation Sample                          Ratio per         Percent                          100 Parts Weight per                                            of Total     COMPONENT     Ref    Polymer   Batch Mix                                            Mix     ______________________________________     Sawdust (40 U.S. Mesh)                   a      100         50   Lbs  48.78%     Ceramic Cenospheres                   b      0           0         0%     Thermoplastic PVC                   c      100         50        48.78%     Depitched Tall Oil                   d      5           2.5       2.44%     Chemical Blowing Agent                   e      0           0         0%     TOTAL, All Components                          205    Parts                                      102.5                                           Lbs. 100%     ______________________________________     References:     (a) Comingled wood fiber/thermoset mix (treated) particles screen sized to      40 US mesh, dried to 4% moisture content by weight.     (b) Ceramic cenospheres  none in this formulation.     (c) Thermoplastic polymer  rigid polyvinyl chloride compound  powder.     (d) Depitched tall oil, BC Chem JC30, add no. 154.     (e) Chemical blowing agent  Hydrocerol BIH  none in this formulation.

Example No. 3 is illustrated by the data shown in the table below. This example divulges a materials blend formulation and the results for comparison of properties and improvements against the Examples No. 1 and 2. This third example contains a proportional amount of depitched tall oilat a ratio of 5% by weight, based on the combined weight of the co-mingled wood fiber-thermoset mixture (treated) fiber sawdust and the ceramic cenospheres (waste by-product of coal-fired electrical power generation facilities--produced by TransAlta Utilities, Keephills, Alberta, Canada (amongst other sources) filler components. The thermoplastic polymer is a typical rigid PVC powdered profile extrusion grade formulation. This formulation contains no other extrusion process additives.

This example illustrates that addition of the depitched tall oil and ceramic cenospheres may result in a marked improvement in extrusion processability and output gains with improved physical properties and a reduction in the density of the final product. The improved outputs may beattributable to the tall oil and cenospheres lubrication and stabilization effect on the polymer melt and the improvement in extrusion fluxing of thematerials with a consequent increase in the viscosity enabling a higher flow rate and reduced back pressure through the extruder die. Bonding of the sawdust filler and cenospheres to the thermoplastic polymer may also show improvement through the increases in strength and shear properties ofthe composite material. The reduced density is a result of the volumetric efficiency and the syntactic effect of the cenospheres in their replacement of solid polymer and sawdust filler for a specific product constant volume.

    ______________________________________     Wood Fiber/Cenospheres and Thermoplastic Polymer     Example No. 3     Formulation for Typical Blend for Evaluation Sample                          Ratio per         Percent                          100 Parts Weight per                                            of Total     COMPONENT     Ref    Polymer   Batch Mix                                            Mix     ______________________________________     Sawdust (40 U.S. Mesh)                   a      50          25   Lbs  24.39%     Ceramic Cenospheres                   b      50          25        24.39%     Thermoplastic PVC                   c      100         50        48.78%     Depitched Tall Oil                   d      5           2.5       2.44%     Chemical Blowing Agent                   e      0           0         0%     TOTAL, All Components                          205    Parts                                      102.5                                           Lbs. 100%     ______________________________________     References:     (a) Comingled wood fiber/thermoset mix (treated) particles screen sized to      40 US mesh, dried to 4% moisture content by weight.     (b) Ceramic cenospheres  TransAlta Utilities (Keepshill Power Plant)  see      Table No. 3 and 4.     (c) Thermoplastic polymer  rigid polyvinyl chloride compound  powder.     (d) Depitched tall oil, BC Chem JC30, add no. 154.     (e) Chemical blowing agent  Hydrocerol BIH  none in this formulation.

Example No. 4 contains no ceramic cenosphere fillers. This example containsa waste wood fiber-thermoset bonded MDF particleboard moulding sawdust, pre-treated with the wood fiber content being adhesive and pressure bondedby a phenolic formaldehyde thermoset binding component. This organic fillercomponent material is thus referred to as being "treated" and "co-mingled".

The organic filler was sized to equivalent generic "un-treated" sawdust grade 4020 specifications as shown previously in the Table No. 5. This fourth example contains a proportional amount of depitched tall oil component at a ratio of 5% by weight, based on the weight of the sawdust component. A chemical blowing agent is added, proportional in amount to the thermoplastic polymer component at a ratio of 3% by weight, based on the weight of the polymer component.

    ______________________________________     Wood Fiber, Thermoplastic Polymer & Chemical Blowing Agent     Example No. 4     Formulation for Typical Blend for Evaluation Sample                          Ratio per         Percent                          100 Parts Weight per                                            of Total     COMPONENT     Ref    Polymer   Batch Mix                                            Mix     ______________________________________     Sawdust (40 U.S. Mesh)                   a      100         50   Lbs  48.08%     Ceramic Cenospheres                   b      0           0         0%     ThermopIastic PVC                   c      100         50        48.08%     Depitched Tall Oil                   d      5           2.5       2.40%     Chemical Blowing Agent                   e      3           1.5       1.44%     TOTAL, All Components                          208    Parts                                      104.0                                           Lbs. 100%     ______________________________________     References     (a) Comingled wood fiber/thermoset mix (treated) particles screen sized to      40 US mesh, dried to 4% moisture content by weight.     (b) Ceramic cenospheres  none in this formulation.     (c) Thermoplastic polymer  rigid polyvinyl chloride compound  powder.     (d) Depitched tall oil, BC Chem JC30, add no. 154.     (e) Chemical blowing agent  Hydrocerol BIH.

This example of the invention illustrates that without the addition of the cenospheres filler, the results are marginally better than the Example No.3 with some minimal physical properties improvement. The improvement in lower density over Example No. 3 may be attributable to the chemical blowing agent producing voids in the thermoplastic polymer matrix. The reduced density may be a result of the volumetric efficiency of the gaseous cells formed in processing and their replacement of solid polymer and sawdust filler for a specific product constant volume. Some improvement in properties of Example No. 4 is thus attributable to the enhanced cellular nature of the thermoplastic polymer matrix providing limited increases in stiffness, strength and shear properties of this example. A given mass of this formulated material blend would produce a significant increase of product volume (at a given cross-sectional area), over that of a comparative mass of solid rigid PVC polymer or that of the formulations of Example No. 2 and Example No. 3 with the same section area.

Example No. 5 is illustrated by the data shown in the table below. This example divulges a materials blend formulation and the results for comparison of properties and improvements against the Examples No 2, 3 and4. This fifth example contains a proportional amount of depitched tall oil component at a ratio of 5% by weight, based on the combined weight of the co-mingled wood fiber-thermoset mixture (treated) fiber sawdust and the ceramic cenospheres (waste by-product of coal-fired electrical power generation facilities--produced by TransAlta Utilities, Keephills, Alberta, Canada amongst other sources) filler components. The thermoplastic polymer is a typical rigid PVC powdered profile extrusion grade formulation. A chemical blowing agent is added, proportional in amount to the thermoplastic polymer component at a ratio of 3% by weight, based on the weight of the polymer component.

    ______________________________________     Wood Fiber/Cenosphere Fillers, Thermoplastic Polymer &     Example No. 5     Chemical Blowing Agent     Formulation for Typical Blend for Evaluation Sample                          Ratio per         Percent                          100 Parts Weight per                                            of Total     COMPONENT     Ref    Polymer   Batch Mix                                            Mix     ______________________________________     Sawdust (40 U.S. Mesh)                   a      50          25   Lbs  12.02%     Ceramic Cenospheres                   b      50          25        12.02%     Thermoplastic PVC                   c      100         50        24.04%     Depitched Tall Oil                   d      5           2.5       2.40%     Chemical Blowing Agent                   e      3           1.5       1.44%     TOTAL, All Components                          205    Parts                                      104.0                                           Lbs. 100%     ______________________________________     Components     ______________________________________     References     (a) Comingled wood fiber/thermoset mix (treated) particles screen sized to      40 US mesh, dried to 4% moisture content by weight.     (b) Ceramic cenospheres  TransAlta Utilities (Keepshill Power Plant )  see      Table No. 3 and 4.     (c) Thermoplastic polymer  rigid polyvinyl chloride compound  powder.     (d) Depitched tall oil, BC Chem JC30, add no. 154.     (e) Chemical blowing agent  Hydrocerol BIH.

This embodiment of the invention illustrates that with the addition of the cenospheres filler and the chemical blowing agent, the results are better than the Example No. 3 and No. 4 with enhanced physical properties improvement. The improvement in lower density over Example No. 3 may be attributable to the chemical blowing agent producing voids in the thermoplastic polymer matrix. The reduced density may be a result of the volumetric efficiency of the gaseous cells formed in processing and their replacement of solid polymer and sawdust filler for a specific product constant volume.

The improvement in properties of Example No. 5 over Example No. 4 is thus attributed to the enhanced cellular nature of the thermoplastic polymer matrix and the syntactic effect of the cenosphere filler providing an increase in stiffness, strength and shear properties of this example. A given mass of this formulated material blend would also produce a significant increase of product volume (at a given cross-sectional area), over that of a comparative mass of solid rigid PVC polymer or that of the formulations of Example No. 2 and Example No. 3 with the same section area.

The improvement over Example No. 4 may be attributable to the improved cellformation due to the nucleating effect of the ceramic cenospheres and the aid of the tall oil in activating the chemical blowing agent to produce gaseous cells in the thermoplastic polymer matrix. The depitched tall oil component, together with the cenospheres, has aided the thermoplastic polymer to effect a superior fluxed matrix phenomena that shows significant improvement over other examples with the increases in strengthand shear properties most pronounced in this example.

Table No. 14 following summarizes the results of Examples No. 1 through 5. The table provides a comparative data base for each example analyzed. These examples have all been based on the use of the preferred thermoplastic polymer, Polyvinyl Chloride. Polyethylene and Polypropylene are expected to have similar results for these other substitutable thermoplastic polymers, with densities relative to the starting solid thermoplastic materials specific gravity as shown on Example No.

                  TABLE 14     ______________________________________     SUMMARY - TEST SAMPLE COMPARATIVE RESULTS     Physical Properties                    No. 1   No. 2  No. 3 No. 4                                              No. 5     ______________________________________     Density, gm/cc 1.43    1.10   0.95  0.80 0.65     Flexural Strength, psi × 10.sup.3                    10      4      4     3    3     Flexural Modulus, psi × 10.sup.3                    400     300    250   250  300     Tensile Strength, psi × 10.sup.3                    6.0     4.0    4.0   3.5  3.0     Tensile Modulus, psi × 10.sup.3                    450     300    300   250  200     Tensile Elongation, %                    60      25     20    18   15     ______________________________________ 

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
 1. A composite material comprising a product of a combination of materials, the combination of materials comprising:(a) an inorganic filler comprised of ceramic cenospheres; (b) a thernoplastic polymer; and (c) a coupling agent comprised of at least one fatty acid having at least 16 carbon atoms and at least one rosin acid having at least 16 carbon atoms.
 2. The composite material as claimed in claim 1 wherein the coupling agent is comprised of between about 10 to 55 percent by weight of the fatty acids and of between about 5 to 50 percent by weight of the rosin acids.
 3. The composite material as claimed in claim 2 wherein the coupling agent is comprised of between about 35 to 55 percent by weight of the fatty acids and of between about 25 to 50 percent by weight of the rosin acids.
 4. The composite material as claimed in claim 3 wherein the coupling agent is comprised of less than about 40 percent by weight of unsaponifiables.
 5. The composite material as claimed in claim 4 wherein the coupling agent is comprised of less than about 20 percent by weight of unsaponifiables.
 6. The composite material as claimed in claim 5 wherein the coupling agent is comprised of a tall oil.
 7. The composite as claimed in claim 1 wherein the combination of materials further comprises an organic filler comprised of cellulosic material and wherein the thermoplastic polymer has a melt temperature of less than the char temperature of the organic filler.
 8. The composite as claimed in claim 6 wherein the combination of materials further comprises an organic filler comprised of cellulosic material and wherein the thermoplastic polymer has a melt temperature of less than the char temperature of the organic filler.
 9. The composite material as claimed in claim 8 wherein the combination of materials is comprised of the coupling agent in an amount of between about 0.5 to 10 percent by weight of the organic filler and the inorganic filler.
 10. The composite material as claimed in claim 9 wherein the combination of materials is comprised of the coupling agent in an amount of between about 0.5 to 5 percent by weight of the organic filler and the inorganic filler.
 11. The composite material as claimed in claim 8 wherein the organic filler is comprised of wood fibers.
 12. The composite material as claimed in claim 11 wherein the organic filler is comprised of co-mingled wood fibers and a thermoset binding polymer.
 13. The composite material as claimed in claim 12 wherein the organic filler has a particle size of less than or equal to about 40 mesh.
 14. The composite material as claimed in claim 12 wherein the combined organic and inorganic fillers comprise between about 10 and 80 percent by weight of the composite material.
 15. The composite material as claimed in claim 14 wherein the combined organic and inorganic fillers comprise between about 15 and 75 percent by weight of the composite material.
 16. The composite material as claimed in claim 12 wherein the organic filler comprises between about 10 to 90 percent by weight of the combined organic and inorganic fillers and wherein the inorganic filler comprises between about 90 to 10 percent by weight of the combined organic and inorganic fillers.
 17. The composite material as claimed in claim 16 wherein the organic filler comprises about 50 percent by weight of the combined organic and inorganic fillers and wherein the inorganic filler comprises about 50 percent by weight of the combined organic and inorganic fillers.
 18. The composite material as claimed in claim 12 wherein the thermoplastic polymer is comprised of a polyolefin having a melt temperature of less than about 390 degrees Fahrenheit.
 19. The composite material as claimed in claim 18 wherein the polyolefin is selected from the group consisting of polyethylene, polypropylene and polyvinyl chloride.
 20. The composite material as claimed in claim 19 wherein the thermoplastic polymer comprises between about 30 and 75 percent by weight of the composite material.
 21. The composite material as claimed in claim 19 wherein the combination of materials is further comprised of a chemical blowing agent.
 22. The composite material as claimed in claim 21 wherein the combination of materials is comprised of the blowing agent in an amount of between about 0.2 to 5 percent by weight of the thermoplastic polymer.
 23. A process for producing a composite material comprising the step of combining an inorganic filler comprised of ceramic cenospheres, a thermoplastic polymer and a coupling agent comprised of at least one fatty acid having at least 16 carbon atoms and at least one rosin acid having at least 16 carbon atoms, wherein the combining step is performed at a temperature of greater than or equal to the melt temperature of the thermoplastic polymer.
 24. The process as claimed in claim 23 wherein the combining step is comprised of the steps of:(a) first mixing the inorganic filler with the coupling agent such that the coupling agent substantially wets the inorganic filler to produce a wetted filler; (b) second mixing the thermoplastic polymer with the wetted filler such that the thermoplastic polymer is substantially homogeneously blended with the wetted filler to produce the composite material.
 25. The process as claimed in claim 23 wherein the combining step further comprises combining an organic filler comprised of cellulosic material with the inorganic filler, the thermoplastic polymer and the coupling agent and wherein the combining step is performed at a temperature of greater than or equal to the melt temperature of the thermoplastic polymer and less than the char temperature of the organic filler.
 26. The process as claimed in claim 25 wherein the combining step is comprised of the steps of:(a) first mixing the inorganic filler and the organic filler with the coupling agent such that the coupling agent substantially wets the inorganic filler and the organic filler to produce a wetted filler; (b) second mixing the thermoplastic polymer with the wetted filler such that the thermoplastic polymer is substantially homogeneously blended with the wetted filler to produce the composite material.
 27. The process as claimed in claim 26 wherein the coupling agent is comprised of between about 10 to 55 percent by weight of the fatty acids and of between about 5 to 50 percent by weight of the rosin acids.
 28. The process as claimed in claim 27 wherein the coupling agent is comprised of less than about 40 percent by weight of unsaponifiables.
 29. The process as claimed in claim 28 wherein the coupling agent is comprised of a tall oil.
 30. The process as claimed in claim 29 wherein the first mixing step is comprised of mixing an amount of the coupling agent of between about 0.5 to 5 percent by weight of the organic filler and the inorganic filler.
 31. The process as claimed in claim 29 wherein the filler is comprised of wood fibers.
 32. The process as claimed in claim 31 wherein the filler is comprised of co-mingled wood fibers and a thermoset binding polymer.
 33. The process as claimed in claim 32 wherein the first mixing step is comprised of mixing an amount of the combined organic and inorganic fillers of between about 10 and 80 percent by weight of the composite material.
 34. The process as claimed in claim 32 wherein the organic filler comprises between about 10 to 90 percent by weight of the combined organic and inorganic fillers and wherein the inorganic filler comprises between about 90 to 10 percent by weight of the combined organic and inorganic fillers.
 35. The process as claimed in claim 32 wherein the thermoplastic polymer is selected from the group consisting of polyethylene, polypropylene and polyvinyl chloride.
 36. The process as claimed in claim 35 wherein the second mixing step is comprised of mixing an amount of the thermoplastic polymer of between about 30 and 75 percent by weight of the composite material.
 37. The process as claimed in claim 35 wherein the combining step is further comprised of dispersing a chemical blowing agent throughout the thermoplastic polymer prior to the second mixing step.
 38. The process as claimed in claim 37 wherein the dispersing step comprises dispersing an amount of the blowing agent of between about 0.2 to 5 percent by weight of the thermoplastic polymer.
 39. The process as claimed in claim 37 further comprising the step of extruding the composite material at a temperature of less than 390 degrees Fahrenheit. 